The present invention relates to a propulsion air stream deflecting apparatus of an air cushion vehicle or a ground-effect machine (hereinafter referred to as ACV) for controlling the direction of a pressurized air stream, produced by a propeller, for providing a propulsion thrust or steering thrust to the ACV.
Air cushion vehicles are provided with a pressurized air stream deflecting apparatus using a pair of rudders for generating a propulsive thrust. A typical example of such a pressurized air stream deflecting apparatus is disclosed in Japanese Patent (unexamined) Publication No. 52-81815 published on July 8, 1977. The apparatus has a horizontal cylindrical air duct mounted on the rear part of the hull of the ACV and extending in the fore-to-aft direction. A propeller fan is installed in the air duct. The air duct is provided with vertical rudders at the rear end thereof.
The known ACV is steered by turning the rudders to the port or starboard side. To brake the vehicle moving forward, the rudders are manually moved with a considerably large magnitude of force to close the rear open end of the air duct. When the ACV travels at a high speed, it is hard to fully close the rear open end of the air duct and hence there is a disadvantage in that a sufficient breaking force may not be applied to the ACV. When the air duct is closed at the rear end, a substantially annular air guide installed around the rear end of the air duct operates to receive the air stream and turn it in the reverse direction, that is, forwardly of the vehicle, as will be described hereinafter in more detail. The reverse air stream is, however, produced to some degree, even when the ACV is advancing, thus decreasing the propulsion thrust. Moreover, the air guide narrows the cross-sectional area of the path of the pressurized air stream through the air duct, so that the resistance to the air stream is increased, reducing the propulsive thrust. In addition, eddy currents are created in the narrow path at the guide and generate noise.